Embodiments of the inventive concepts described herein relate to a 3-dimensional (3D) optical interconnection structure, and more particularly, to a waveguide of a 3D interconnection structure including a main waveguide and branch waveguides which branch an optical signal and power which are propagated in the main waveguide and an optical data bus system of a 3D interconnection structure using the same.
Most data interconnection between multi-chips, such as between a central processing unit (CPU) and a memory, depends on an electric data bus system. However, there is a limit in a signal transmission speed due to serious power dissipation in an electric transmission line and a cross-talk by interference between transmission lines.
To improve this, a conventional optical data bus system using not electric connection but an optical signal is proposed. U.S. Pat. No. 8,526,816 discloses a structure for increasing a signal transmission speed using an optical data bus without interference between channels.
However, the conventional optical data bus system uses a reflector or an optical grating coupler to branch an optical signal. There is a disadvantage in that additional optical loss occurs due to low coupling efficiency and a large alignment error in connection between the optical grating coupler and a waveguide.
It is needed to provide an optical data bus system of a 3D interconnection structure without loss and an alignment error by optical coupling by additionally locating branch waveguides, each of which forms a small angle, on a conventional waveguide.